Blasting cartridge



Patented May 26, 1931 I UNITED STATES PATENT OFFICE FRANK ARMSTRONG, OF CHICAGO, ILLINOIS, ASSIGNOR TO SAFETY MINING GOM- PAINY, OF CHICAGO, ILLINOIS, A CORPORATION BLASTING CARTRIDGE Application filed April is,

The present invention relates to blasting cartridges of the general type shown in patents to Crawford, Helmholtz and Ferrell No. 1,632,887 and Ferrell, Helmholtz and Crawford N 0. 1,610,274. Cartridges of this general type comprise a rigid casing which is.

adapted to receive a charge of a suitable liquefied gas and which has a pressure responsive venting means for the purpose ofliberating the confined gas when the pressure within the casing reaches a predetermined the purpose of converting the charge to the.

gaseous state and thereby cause the desired increase in pressure. In the patents referred to and also in the present instance, this heating means is adapted to be energized bymeans of a fusable electric conductor when used with a suitable source of electricity. 1

More particularly, the present inventionrelates to a novel means for normally maintaining a short circuited condition within the cartridge for the purpose of preventing accidental or premature discharge thereof and in this respect, the present invention 'is in the nature of an improvement upon the invention shown and described in the application of David Hodge, Serial No. 336,419, filed January 31, .1929.

In the use of cartridges of the above type, it has been found that there is considerable danger of accidental explosion due to the terminals of the cartridge coming into contact with a source of electricity through accident or carelessnessTTor this reason, it is highly desirable to provide some means wherebythe electric circuit, including the heating 'nilean's 1929. Serial No. 356,360.

within the cartridge, is rendered inoperative until such time as cartridge is positioned within the drill hole and in condition to be discharged.

One of the principal olqjects of this invention, therefore, is to provide an improved means for safeguarding against unintentional or accidental discharge of cartridges of this type.

More particularly, it is an object of the present invention to provide means for normally maintaining a short circuited condition within the cartridge-and requiring a positive manual act on the; part ofthe operator to remove such condition. y

Specifically, it is an object of the invention to provide a short circuiting means which is operable when the cartridge cap is removed, but which is rendered inoperative when the ca is applied to the cartridge'casing.

t is also an object of the invention to generally improve the construction and design of the cartridges of this type, with part1cular reference to the construction and arrange ment of pressure resisting packings and the composition and arrangement of insulating elements for effectively isolating the conducting elements ofthe cartridge.

Other objects and advantages of the present invention will become apparent from the following description of the accompanying drawings, wherein,

Fig. 1 is a view in longitudinal section of the charging end of .the present improved cartridge and having a charging mechanism at one end.

thereof communicating with the chamber and a discharge cap at the other end thereof, which is separated from the chamber by means of a rupturable wall. The charging end of the cartridge embodies an axially arranged electrode which is suitably insulated from the casing and which additionally serves as a valve mechanism 'for permitting its opposite end with the casing through the medium of the rupturable metallic disc secured over the end of the casing. Thus, it

y will be apparent that a complete circuit exvists from the electrode through the heating device to the casing and it is this circuit to which my improved short circuiting means is applied for the purpose of preventing accidental discharge of the cartridge in the event that the electrode and the casing should unintentionally come into contact with a source of electricity. The cap for the charging end of the cartridge is adapted to receive two electrical conductors which are suitably insulated from each other and the cap embodies means for placing the respective c onduc- 1 tors in current transmitting relation with the electrode and the cartridge casing respective- 1y when the cap is applied to the casing an the cartridge is in condition to be discharged. It is apparent that the electrode and casing should not be short circuited when the cap is in place on the cartridge and I have therefore provided means for breaking the short circuited relation by the application of the cap to the cartridge.

With the above general outline of my invention in mind, the details of construction and their mode of operation should be readilyunderstood from' an inspection of" the drawings. Referring specifically to the drawings, it will be observedthat the charge receiving chamber 2 tapers inwardly at its opposite ends as indicated at 3 and 4 toward the approach openings 5 and 6 located at the charging and discharging ends respectively. The approach openings 5 and 6 constitute restricted portions, beyond which are hollow cylindricalextensions 7 and 8 respectively. These extensions are suitably threaded or otherwise formed for the reception of.

caps 9 and 10 respectively. Electrode 14 extends axially through the approach opening 5 and is insulated therefrom by means of a combined insulating and heat and ressure resisting packing 11 which is preferably formed of moulded asbestos. A split steel rin 12 is provided to assist in holding the pac ing 11 in place and to prevent the access of high pressure directly thereto. The electrode 14 is provided with an enlargement 15 between which and the packing 11 is interposed an insulating fibre washer 16 and annular steel ring 16. The electrode is further insulated from the outer end of the 0 ening 5 by means of a fibre bushing 13. A f ibre disc 17 and clamping nut 18, both threaded upon the electrode, serve to clamp the electrode' in place within the opening and to suitably compress the packing between shoulder 15 and the disc 17. In this connection, it will be noted that disc 17 serves to insulate the clamping nut 18 from the casing.

The electrode above described is so con structed as to serve the further purpose. of a valve through which the explosive charge may be introduced into the casing. For this purpose, the electrode is provided with an axial bore 20 which is enlarged intermediate its ends and provided with a conical valve seat 23. A valve member 21 isslidably disposed within the enlarged portion of the bore and is normally urged into engagement with the valve seat by means of a spring 24 which is interposed between the valve member and the abutment 'plug 25 screw threaded in the inner end of the electrode. valve member 21 is provided on its peripheral surface with longitudinal grooves 22forpermitting-the passage of fluid thereby when the member is forced away from the valve seat 23. An' outlet port 25 places the enlarged port-ion of the valve bore in communication d with the chamber'2. The outerend of the electrode is externally screw threaded for the reception of a correspondingly threaded valve cap 26.

The improved short circuiting device con- The sists essentially in a pairof metallic discs 19 and 19 which have electrical connection with the electrode and cas'ing respectively and which are adapted to be normally moved to and held in contacting relation. The disc 19 is'screw threaded upon the electrode ad acent to the clamping nut 18. The disc 19 is slid-.

ably disposed within the hollow extension 7 of the casing and is arranged to be moved axially therein into contact relation with the disc 19 by means of a metallic spring which is interposed between the disc 19' and the wall of the restricted portion of the casing. Thus, the disc 19 is in direct electrical contact with the electrode 14 and the disc 19 is in electrical connection with the casing through the medium of the spring so that a short circuited condition exists when these two discs'are' in contact.

In order that the short circuit may be broken. when it is desiredto place the car- 'tridge inoperative relation to a drill hole and to discharge same, the cap 9 is provided with a cylindrical extension which engages the a disc 19 when the cap is applied to the cas ing and screwed up into position thereon.

In this Way the short circuit is broken when the cap and easing are in assembled relation and ready for use, but the short circuited condition exists at all times prior to the application of the cap to the casing. i

For the purpose of conducting electricity to the two electrodes, namely, the casing and the centrally arranged electrode 14, the cap 9 is provided with openings for the reception of two electricity conductors. The conductor for one of said openings is insulated from the cap by means of a fibre bushing 34, while the other has direct metallic connection with the cap as at 35 and is adapted to be clamped in place by setscrew 36. The latter conductor, therefore, is in direct electrical connection with the cartridge casing. The other conductor passes through an opening 33 in the insulating cup 28 and engages within the open ing 31 in a metallic plug which is centrally arranged within the insulating cup 28. A setscrew 32 is provided for holding the second conductor in the plug 30 and this setscrew is suitably insulated from the body of the capby means of a fibre sleeve 37. The circuit between the metallic plug 30 and the electrode 14 is completed by means of a spring which bears at one end on the plug and at its opposite end on the metallic valve cap 26. Thus, it is apparent that when the cap is assembled on the cartridge casing the cables v of firmly holding the shear ring, the rupturor conductors carried by the cap are placed in electrical connection with the electrode 14 and the cartridge casing 1 respectively and that at this time the short circuiting discs 19 and 19 are moved out of engagement.

The discharge end of the cartridge is provided with an annular seat 38 for the reception of the'rupturable disc 39 and a shear ring 40. A packing, preferably in the form of a fibre gasket, is provided intermediate the disc 39 and the transverse wall of the annular recess 38 for the purpose of effectively sealing the opening which is closed bythe disc 39 against the escape of pressure until such time as the disc is ruptured. The discharge cap 10 is threaded or otherwise secured in the end of the casing and is arranged in abutting relation to the shear ring 40 for the. purpose able disc and the-fibre'gasket in place. The discharge cap is provided with a central chamber 43 and a plurality of radial discharge orts 44.

It is helieved that the operation of my improved blasting cartridge will be apparent from the foregoing description and that a brief outline of the o erationat this point will be sufficient. It w1ll,of course, be understood that the cap 9 must beiremoved in order to charge the cartridge. The charging is effected by simply removing the cap,9 and the L valve cap 26 and introducing the liquefied gas into the cartridge through the valve 21. The normal procedure is to then transport the charged cartridge to the location where it is to be used and to insert it into a drill hole provided therefor. The cap 9 is not applied until after the cartridge has been so positioned inav drill hole and is ready to be pushed back into position within the hole and be discharged. It will be observed that during this entire period of handling and transportation of thecartridge the discs 19 and 19 are in engagment and that the circuit in-- cluding the casing, the electrode and the heating device is therefore short circuited so that any accidental contact with a source of electricity will do no damage. When it is desired to discharge the cartridge, the cap 9 is applied thereto, thus breaking the contact bietween discs 19 and 19 and establishing contact. between the two conductors carried by the cap and the electrode and casing respectively. The cartridge is then pushed back in the drill hole and the circuit including a source of electricity may be closed in any desired manner to effect the discharge of the cartridge. 7

Although I have shown herein the'specific construction and described the same in considerable detail, it is to be understood that this has been done principally for purposes of illustration and that the invention in its broader aspects is not to be construed as being confined to precise details shown and described but that the same is susceptible of considerable modification within the scope of the invention.

Having now fully described my invention, what I claim is:

1. A blasting cartridge comp-rising a casing, an electrode projecting axially through an end of said casing, and insulated therefrom, a metallic disc secured-to saidelectrode, a second metallic disc carried by said casing and movable axially into and out of contact with the first said disc, spring means tending to establish and maintain contacting relation of said discs and manually operable means for breaking said relation.

2. A blasting cartridge comprising a casing, an electrode projecting axially through an end of said casing and insulated there: from, a metallic disc secured to said electrode, a second metallic disc carried by saidcasing and movable axially into and out of contact with the first said disc, spring means tending to establish and maintain contacting relation of said discs, a cap adapted to be detachably secured to said casing and having means for moving said movable disc out of- I engagement with said fixed disc.

3. A blasting cartridge comprising a hollow 0 lindrical body, a shoulder formed internal ly of said body adjacent an end thereof,

a rupturable disc adapted to be positioned on said shoulder, said body being internally screw threaded outwardly of said shoulder, and a discharge cap threaded into the end of said body and serving to hold said disc in sealing engagement with said shoulder.

4. A blasting cartridge comprising a hollow cylindrical body, a shoulder formed internally of said body adacent an end thereof, a rupturable disc adapted to be positioned on said shoulder, said body being internally screw threaded outwardly of said shoulder and a discharge cap adapted to be engaged in the end of said body and serving to hold said disc in sealing engagement with said.

shoulder, said cap comprising a head portion of an outside diameter substantially equal to that of said body, and a shank portion of reduced diameter provided externally with screw threads. adapted for engagement with the threads in said body, said shank portion having an axial bore, and a plurality of radial ports in said head portion communicating with said bore.

5. A blasting cartridge comprising a hollow cylindrical body, a transverse wall formed intermediate the ends of said body and having a central opening therethru, an

electrode extending thru said opening, means for insulating the electrode from said body and sealing the same on said body to prevent the escape of gas, ,theinterior of said 'body beyond said wall being provided with screw threads, a terminal cap having a head portion of an outside diameter substantially equal to that of said body, and a shank por- W tion of reduced diameter provided externally with screw threads adapted for engagement with the threads in said body, said terminal V cap embodying means for placing said electrode and cartridge body, respectively, in circuit with a source of electricity.

6. A blasting cartridge comprising a substantially cylindrical metallic body, a transverse wall intermediate the ends of said body, an electrode extending thru said wall and insulated therefrom, a contact element on said electrode adjacent the outer end thereof, a second contact element surrounding said electrode and positioned intermediate said wall and the first said contact element, means for normally urging said second contact into engagement with the first said contact, and a terminal cap applicable to the'end of said bodyan d having means for moving said contacts out of en agement. v 7. A blasting cartri ge emboyding a gas chamber, an electrode extending thru a wall of said chamber and insulated and sealed passes? plunger iii'sealing position, and said plunger ,7

with respect thereto, said electrode being provided with an axial bore and a communicating gas passage of smaller diameter than the bore, a plunger slidably mounted in said bore and adapted to seal the end of said gas a springfifor normally holding said aving longitudinal grooves to 'permit ,the i 

